The present invention relates to a canister for a vehicle, and more particularly to a canister serving as evaporated fuel adsorbing means used for treating evaporated fuel from a fuel system in an internal combustion engine mounted on a vehicle.
In conventional, in the vehicle, there has been employed an evaporated fuel treating apparatus for preventing evaporated fuel from a fuel system such as a fuel tank or the like from being discharged to an atmospheric air, and a structure shown in FIG. 7 has been, for example, known as means for adsorbing and collecting the evaporated fuel.
A canister 101 shown in FIG. 7 is structured such as to introduce an evaporated fuel generated within a fuel tank 103 from an introduction port 104 so as to flow through a first adsorbing material layer 105 constituted by adsorbent such as activated carbon or the like, a communicating chamber 106, a second adsorbing material layer 107 and a third adsorbing material layer 108, adsorb and collect the evaporated fuel to each of the adsorbing material layers 105, 107 and 108 and discharge air from an atmospheric air port 110 through a chamber 109 at a time when an engine 102 stops, and, at a time when the engine 102 is operated, such as to apply a negative pressure generated in an intake manifold 111 to a purge port 112 of the canister 101 so as to purge the evaporated fuel adsorbed and collected to each of the adsorbing material layers 105, 107 and 108 to the engine 102 from the purge port 112. In the drawing, reference numeral 113 denotes a filter and reference numeral 114 denotes an air cleaner.
In the conventional canister, when the engine 102 stops, the evaporated fuel is adsorbed to each of the adsorbing material layers 105, 107 and 108 in the canister 101, however, an adsorbing state immediately after the engine stops corresponds to a state, as shown in FIG. 8, that concentration of adsorption is high in the first adsorbing material layer 105, concentration of adsorption is middle in the second adsorbing material layer 107 and concentration of adsorption is low in the third adsorbing material layer 108. In this case, in the first adsorbing material layer 105 and the second adsorbing material layer 107 in FIG. 8, the adsorbing material layer having high concentration is expressed by a narrowly hatched portion.
Then, since the evaporated fuel adsorbed to each of the adsorbing material layers 105, 107 and 108 tends to uniformly diffuse to a whole together with passage of time after the engine stops, the concentration of the evaporated fuel within the third adsorbing material layer 108 becomes gradually higher as shown in FIG. 9, so that all of the adsorbing material layers 105, 107 and 108 have the substantially uniform concentration. In FIG. 9, intervals between the hatched lines expressed within the respective adsorbing material layers 105, 107 and 108 are set to the same interval, thereby showing a uniform concentration state. When the concentration of the third adsorbing material layer 108 becomes high as mentioned above, a little amount of evaporated fuel adsorbed to the third adsorbing material layer 108 may leak to the chamber 109 even if the adsorbing material layer 108 can yet adsorb some evaporated fuel, so that there is a risk that the evaporated fuel leaks to the atmospheric air through the atmospheric air port 110 and the canister dose not have an ability to adsorb and collect the sufficient evaporated fuel.
An object of the present invention is to provide a canister for a vehicle which can further reduce a leakage of an evaporated fuel to an atmospheric air and can sufficiently adsorb and collect the evaporated fuel.
In order to solve the problem mentioned above, in accordance with the present invention, there is provided a canister for a vehicle comprising:
an introduction port for an evaporated fuel provided in a casing;
an atmospheric air port for the evaporated fuel provided in the casing; and
an adsorbing material layer communicating between the introduction port and the atmospheric air port,
wherein a chamber is provided between the atmospheric air port and a surface on a side of the atmospheric air port in the adsorbing material layer, and a leakage preventing adsorbing material layer is arranged within the chamber so that a space layer is formed between the leakage preventing adsorbing material layer and the surface on the side of the atmospheric air port in the adsorbing material layer and another space layer is formed between the leakage preventing adsorbing material layer and the atmospheric air port.
In accordance with the present invention, when the engine stops, the evaporated fuel generated from an evaporated fuel generating source is adsorbed and collected to the adsorbent in the adsorbing material layer within the canister from the introduction port. At this time, immediately after the engine stops, the closer to the introduction port a part in the adsorbing material layer within the canister is, the higher concentration of adsorption is. However, in correspondence to passage of time after the engine stops, the evaporated fuel diffuses to a whole of the adsorbing material layers within the canister and leaks out from the surface on the side of the atmospheric air port in the adsorbing material layer only at a little amount.
At this time, since the space layer is provided between the surface on the side of the atmospheric air port in the adsorbing material layer and the leakage preventing adsorbing material layer, the leakage of the evaporated fuel can be restricted by this space layer.
Further, it is possible to adsorb and collect and the evaporated fuel leaking within the space layer by providing the leakage preventing adsorbing material layer.
Accordingly, it is possible to significantly reduce an amount of the evaporated fuel within the adsorbing material layers which is discharged to the atmospheric air through the atmospheric air port.
Further, in accordance with the present invention, the leakage preventing adsorbing material layer may be formed by a filter including adsorbent to which an adsorbent is penetrated.
In accordance with this structure, since an amount of the evaporated fuel leaking from the surface on the side of the atmospheric air port in the adsorbing material layer is a little as mentioned above, an amount of the leakage preventing adsorbent required for adsorbing the leaking evaporated fuel can be reduced. Accordingly, as well as the function can be sufficiently achieved by the leakage preventing adsorbent penetrating into the filter in the manner mentioned above, the leakage preventing adsorbing material layer can be constituted only by placing the filter into which the leakage preventing adsorbent penetrates, so that a structure for assembling the leakage preventing adsorbent becomes simple and an operation for assembling becomes significantly easily performed.